The proposed research contains two programs. One is an investigation of amalgamation reaction using Ag-Sn-X alloys (where X is an additional element). The second is an investigation of dissolution mechanism of constitutent elements from amalgam alloys (Ag-Sn plus X). During the current year, the amalgamation reaction research was extended to two commercial high copper amalgam alloys, Tytin (S.S.White) and Sybraloy (Kerr). Analysis of mercury plated tablet specimens with a scanning electron microscope equipped with a x-ray energy dispersive analyzer revealed only gamma-one polyhedra and tiny Cu6Sn5 crystals (l micromoles on these alloys. No gamma-two crystals were detected in these specimens. In the dissolution experiments, Ag was found to enter mercury from Ag3Sn with a rate constant of about 10 to the minus 4th power cm/sec. Tin from Ag3Sn, on the other hand, reached only 1/50 of saturation in the time required for Ag to reach saturation. BIBLIOGRAPHIC REFERENCES: M.Marek, T. Okabe, and R.F. Hochman, "In Vitro Corrosion of Dental Amalgam Phases", J. Biomed. Mater. Res., 10, 789 (1976). C.F. Timmons, A.L. Hines, G.R. Lightsey and T. Okabe, "Diffusion of Mercury in Ag2Hg3 from Weight Loss Data", J. Biomed. Mater. Res., 10, 371 (1976).